Black pepper (Piper nigrum) is a common remedy in Traditional Chinese Medicine and possesses diverse biological activities including anti-inflammatory properties. Osteoarthritis (OA) is a degenerative joint disease with an inflammatory component that drives the degradation of cartilage extracellular matrix. The present study aimed to assess the effects of piperine, the active phenolic component in black pepper extract, on human OA chondrocytes. In this study, human OA chondrocytes were pretreated with piperine at 10, 50 or 100μg/ml and subsequently stimulated with IL-1β (5ng/ml) for 24h. Production of PGE2 and NO was evaluated by the Griess reaction and an ELISA. Gene expression of MMP-3, MMP-13, iNOS and COX-2 was measured by real-time PCR. MMP-3 and MMP-13 proteins in culture medium were determined using cytokine-specific ELISA. Western immunoblotting was used to analyze the iNOS and COX-2 protein production in the culture medium. The regulation of NF-kB activity and the degradation of IkB were explored using luciferase and Western immunoblotting, respectively. We found that piperine inhibited the production of PGE2 and NO induced by IL-1β. Piperine significantly decreased the IL-1β-stimulated gene expression and production of MMP-3, MMP-13, iNOS and COX-2 in human OA chondrocytes. Piperine inhibited the IL-1β-mediated activation of NF-κB by suppressing the degradation of its inhibitory protein IκBα in the cytoplasm. The present report is first to demonstrate the anti-inflammatory activity of piperine in human OA chondrocytes. Piperine can effectively abrogate the IL-1β-induced over-expression of inflammatory mediators; suggesting that piperine may be a potential agent in the treatment of OA.
Keywords: Inflammation; NF-κB; Nitric oxide; Osteoarthritis; Piperine.